Environmental impact of three different engineering thermoplastics: How much does it change when using recycled polyamide?

Thermoplastic compounds are used in several industrial, domestic and consumer applications. Thanks to their strength, lightness, flexibility and processing properties, they are also widely used for engineering purposes (EngTh). However, thermoplastics are often derived from polymers formed from non-renewable sources, such as oil. In addition, the production processes have a high consumption of energy. This research aims to evaluate the environmental impacts with the Life Cycle Assessment methodology of three polymers based on polyamide 6.6 modified with flame retardants (brominated polystyrene and antimony trioxide, aluminium diethylphosphinate and melamine polyphosphate, red phosphorus) and the influence of the replacement of the oil-based polyamide 6.6 with mechanical recycled polyamide on the sustainability of the production. The analysis was conducted using SimaPro v9.5 software, Ecoinvent 3.9.1 database and ReCiPe 2016 v1.07 impact assessment method. The primary data was collected in 2023 in a facility located in Italy. The results show that the impact of raw materials accounts for more than 95% of the environmental profile in all three products considered, while the processes for the production and the subsequent transports are no more than 5%. The analysis highlighted that up to 6-9% of environmental benefits can be achieved by replacing only 10% of oil-based PA 6.6 with mechanical recycled PA (MRPA), with the best results for RPm given the highest percentage of PA 6.6 in the initial mixture. The results of this assessment will be useful to promote the production of EngTh more sustainably.